I just started thinking about reinstalling my hard top,
but the head liner is falling off.
I know I can pull it down and leave it but I was wondering
what others have done to reline it?

I have seen indoor/outdoor carpet used quite effectively - just glued to the underside of the lid!

I used 3/8 Felt that I found at a Hardware store I just made it stick with a can of adhesive looks good

If you have a '40 and are into the "original" look, CCOT used to offer a replica headliner. Had it installed on my hard top and it looks great.

I tried to use the CCOT liner and it looked like shit. It was a total PITA.

I ended up Hurculining it and it looks awesome.

I showed the liner to three upholstery shops before I found one that thought they could work with it. This shop did lots of custom upholstery on 40' and 50's hotrods and was used to working with older-style materials. So, it's not an easy installation, I guess. It might be a good idea to consider a professional upholsterer or restoration shop if you decide to go with the CCOT kit.